Do not include the whole ActionView::Helpers::UrlHelper module

lib/gitlab/email/message/in_product_marketing/base.rb

@@ -50,7 +50,7 @@ module Gitlab
           def cta_link
             case format
             when :html
-              link_to cta_text, group_email_campaigns_url(group, track: track, series: series), target: '_blank', rel: 'noopener noreferrer'
+              ActionController::Base.helpers.link_to cta_text, group_email_campaigns_url(group, track: track, series: series), target: '_blank', rel: 'noopener noreferrer'
             else
               [cta_text, group_email_campaigns_url(group, track: track, series: series)].join(' >> ')
             end
@@ -89,7 +89,7 @@ module Gitlab
             case format
             when :html
               links.map do |text, link|
-                link_to(text, link)
+                ActionController::Base.helpers.link_to(text, link)
               end
             else
               '| ' + links.map do |text, link|

lib/gitlab/email/message/in_product_marketing/helper.rb

@@ -7,7 +7,6 @@ module Gitlab
         module Helper
           include ActionView::Context
           include ActionView::Helpers::TagHelper
-          include ActionView::Helpers::UrlHelper
 
           private
 
@@ -32,7 +31,7 @@ module Gitlab
           def link(text, link)
             case format
             when :html
-              link_to text, link
+              ActionController::Base.helpers.link_to text, link
             else
               "#{text} (#{link})"
             end